The invention relates to a reservoir or accumulator loading valve, and more particularly to a loading valve of the type wherein a pre-control valve subjected to pressure of a reservoir circuit, the pre-control valve controlling a switching valve depending on this pressure and the switching valve having a piston controlling the connection between a pump and a working hydraulic circuit while the reservoir circuit is supplied with pressure fluid via a flow control diagram and a check valve.
Such a reservoir loading valve is known from German Patent Publication No. 30 34 457, in which the reservoir circuit is supplied with pressure fluid via a loading conduit which branches off from a conduit leading from the pump to the switching valve. The loading conduit the direction of flow has a flow control orifice and a check valve. If the switching valve keeps the connection between the pump and the working hydraulic circuit open and if the same is supplied with pressure fluid there exits also a connection between the working hydraulic circuit and the reservoir circuit so that pressure peaks occuring in the working circuit may be propagated into the reservoir circuit. Such pressure peaks which may exceed the maximum pressure of the resevoir preset and a pre-control valve by a considerable amount are damped by the reservoir or accumulator. However, the reservoir thereby receives each time a corresponding pressure fluid volume so that its pressure may increase well beyond the desired maximum pressure. This must be taken into consideration when designing the reservoir as far as strength requirements and the necessary safety precautions are concerned. Depending on the design of the valves in the reservoir circuit, and on other circumstances, additional measures must be taken to protect the same against this pressure. Furthermore, with the above-described arrangement of the known reservoir loading valve it is not possible to operate the working hydraulic system with higher pressures than the maximum permissible reservoir pressure.
It is, therefore, an object of the present invention to provide a reservoir loading valve followed by a working hydraulic system, in which the reservoir circuit is not subject to pressure peaks beyond a pre-determined maximum permissible pressure. Furthermore, it is an object of the present invention to operate the working hydraulic system with any desired pressure without influencing the reservoir circuit.